Here is an enlightening quote from the article addressing a possible cause of their success,
"Many of today's Pentecostals were brought into the faith by other Pentecostals. But new converts also come on their own to the doors of churches or the homes of pastors. For those in gangs, who conclude that their only way out is death or jail, conversion offers a third option, says David Smilde who studies the phenomenon in Caracas, Venezuela, and is the author of "Reason to Believe," published this past summer.
"It's a way of stepping out of an impossible situation; they are no longer feared by the [criminal] network," says Mr. Smilde, a sociologist at the University of Georgia. Where there is little police presence or institutional support, he says, "Pentecostalism is one way out."
"The only path to live in peace is this path," agrees Thiago de Castro Cosia, a young convert from New Zion. "It's the only way to make your enemies your friends. It's the only way to be free."
http://www.csmonitor.com/2007/1218/p01s02-woam.html?page=1